Simple python asyncio example.

test_asyncio.py

"""
This program defines a run_all function which will retrieve two
URLs and run a shell subcommand, all concurrently, using asyncio.

What stands out in this example is the readability of the get() and cmd()
functions, and the usefulness of asyncio.gather().

An excerpt from the program output shows the way they are interleaved:

    Start: http://google.com
    Start: http://google.com.au
    Start: ls ~/
    Proc created: ls ~/
    Finish: ls ~/
    Finish: http://google.com
    Finish: http://google.com.au

aiohttp is from pypi:

    pip install aiohttp
"""
import asyncio
from asyncio.subprocess import PIPE
import aiohttp

async def get(url):
    print("Start: %s" % url)
    response = await aiohttp.request("GET", url)
    print("Finish: %s" % url)
    response.close()
    return 1

async def cmd(cmd):
    print("Start: %s" % cmd)
    proc = await asyncio.create_subprocess_shell(
            cmd, stdin=None, stderr=None, stdout=PIPE)
    print("Proc created: %s" % cmd)
    out = await proc.stdout.read()
    print("Finish: %s" % cmd)
    return out

async def run_all(url1, url2, shellcmd):
    r1 = get(url1)
    r2 = get(url2)
    s1 = cmd(shellcmd)
    results = await asyncio.gather(r1, r2, s1)

    for res in results:
        print(res)


loop = asyncio.get_event_loop()
loop.run_until_complete(run_all("http://google.com.au", "http://google.com", "ls ~/"))
loop.close()